Additive for fuel oiliness

ABSTRACT

The invention concerns an additive for motive fuel additive, in particular with low sulphur content not more than 500 ppm, consisting for the most part of a combination comprising 5 to 95 wt. % of a glycerol monoester R1-C(O)-O-CH2-CHO-CH2OH or R1-C(O)-O-CH(CH2OH)2, R1 being an alkyl chain containing 8 to 60 carbon atoms, or a monocyclic or polycyclic group comprising 8 to 60 carbon atoms, and from 5 to 95 wt % of a compound of formula R2-C(O)-X, R2 being an alkyl chain containing 8 to 24 carbon atoms, or a monocyclic or polycyclic group comprising 8 to 60 carbon atoms, and X being selected among (i) the groups OR0, R0 being a hydrocarbon radical comprising 1 to 8 carbon atoms, optionally substituted by one or several esters; and (ii) the groups derived from primary or secondary amines and alkanolamines with aliphatic hydrocarbon chain, comprising 1 to 18 carbon atoms.

The present application is a 371 of PCT/FR98/02823 filed Dec. 22, 1998.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fuel containing a lubricity additivefor improving the lubrication properties of fuels, whether groundvehicle engine fuel (diesel) or jet fuel, and more particularly ofdiesel fuels with a low sulphur content.

It is well known that diesel fuels and jet fuels must have lubricatingcapabilities, for the protection of pumps, injection systems and anymoving part with which these products come into contact in an internalcombustion engine. With the intention of employing products which areincreasingly pure and non-polluting, in particular devoid of sulphur,the refining industry has been led increasingly to improve its treatmentprocesses for the removal of sulphur compounds. However, it has beenobserved that on losing sulphur compounds, the aromatic and polarcompounds often associated were also lost, which caused a loss in thelubricating power of these fuels. Thus, beyond certain contents, theelimination of sulphur compounds from the composition of these productsvery substantially promotes the phenomena of wear and of failure ofmoving components in pumps and in injection systems. As regulations inmany countries have imposed a limitation on the acceptable upper contentof sulphur compounds in fuels of 0.05% by weight, in order to lower theemissions of polluting combustion gases from cars, lorries or buses,especially in urban built-up areas, these lubricating compounds must bereplaced by other compounds which are non-polluting with regard to theenvironment but exhibit a sufficient lubricating power to avoid therisks of wear.

The literature also mentions that petrol fuels with a low sulphurcontent have a lubricating power which can prove to be insufficient toensure good lubrication of the injection systems in new vehicles and canbring about a premature risk of wear.

Several types of additives have already been provided in order to solvethis problem. Thus, antiwear additives have been added to diesel fuels,some of these additives being known in the field of lubricants, of thetype of unsaturated fatty acid dimers and fatty acid esters, aliphaticamines, esters of fatty acids and of diethanolamine, and long-chainaliphatic monocarboxylic acids, such as described in U.S. Pat. Nos.2,527,889, 4,185,594, 4,204,481 and 4,208,190. The majority of theseadditives exhibit a sufficient lubricating power but at concentrationswhich are much too high, which is very unfavourable economically forpurchasing. In addition, additives containing dimeric acids, like thosecontaining trimeric acids, cannot be employed in fuels feeding vehiclesin which the fuel can be in contact with the lubricating oil, becausethese acids form, by chemical reaction with the detergents usuallyemployed in lubricants, deposits which can accelerate the wearprocesses.

U.S. Pat. No. 4,609,376 recommends the use of antiwear additivesobtained from esters of mono- and polycarboxylic acids and ofpolyhydroxylated alcohols in fuels containing alcohols in theircomposition.

In Patent GB 2,307,246, the product resulting from the reaction ofcarboxylic acid containing 10 to 60 carbon atoms, chosen from fattyacids or fatty acid dimers, with an alkanolamine, obtained bycondensation of an amine or of a polyamine with an alkylene oxide, ispreferred as lubricity additive.

It is preferable, in Patent GB 2,307,247, to employ an acid derivative,substituted by a least one hydroxyl group or one ester of polyols, oralternatively an amide of this acid.

Another route chosen is to introduce vegetable oils or their esters intothe fuels, in order to improve their lubricating power or theirlubricity. These include rapeseed, linseed, soybean and sunflower oilsor their esters (see Patents EP 635,558 and EP 605,857). However, one ofthe major disadvantages of these esters is their low lubricating powerat a concentration of less than 0.5% by weight in the fuels.

The present invention aims to solve the problems encountered with theadditives provided by the prior art, that is to say to improve thelubricating power of the desulphurized and partially dearomatized fuels,while remaining compatible with the other additives, in particulardetergents, and the lubricating oils, in particular in not formingdeposits, and while reducing the cost price, in particular by a loweradditive content of markedly less than 0.5.

The subject of the present invention is the use as lubricity additivefor improving the lubricating power of diesel and aviation fuels with alow sulphur content, that is to say with a sulphur content of less thanor equal to 500 ppm, characterized in that the additive is composed of:

1) from 5 to 25% by weight of at least one glycerol monoester offollowing formula (I_(A)) or (I_(B)):

 with R₁ chosen saturated or unsaturated, linear or slightly branched,alkyl chains comprising from 8 to 24 carbon atoms and cyclic andpolycyclic groups comprising from 8 to 60 carbon atoms;

2) from 35 to 75% by weight of at least one compound of formula (II)below:

 R₂ is a saturated or unsaturated, linear or slightly branched, alkylchain comprising from 8 to 24 carbon atoms or a cyclic or polycyclicgroup comprising from 8 to 60 carbon atoms and X is chosen from (i) thegroups OR₀, wherein R₀ being a hydrocarbon residue comprising from 1 to8 carbon atoms, optionally substituted by one or more ester groups, and(ii) the groups deriving from primary and/or secondary amines or fromalkanolamines with a linear or branched aliphatic hydrocarbon chaincomprising from 1 to 18 carbon atoms, and

3) from 0.1 to 20% by weight, preferably from 5 to 20% by weight, of atleast one glycerol diester of formula (III_(A)) and/or (III_(B)):

 in which R₃ and R₄, which are identical or different, are chosensaturated or unsaturated, linear or slightly branched, alkyl chainscomprising from 8 to 24 carbon atoms and cyclic and polycyclic groupscomprising from 8 to 60 carbon atoms.

Preference is given, among the glycerol monoesters of formula (I) andthe diesters of formula (III) with, respectively, R₁ or R₃ and R₄consisting of an alkyl chain, to the monoesters and diesters obtainedfrom the oils of the group composed of lauryl oils originating fromcopra or palm, which are rich in saturated alkyl chains containing 12 to14 carbon atoms, palmitic oils resulting from palm, lard or tallow,containing a major amount of saturated alkyl chains containing 16 carbonatoms, linoleic oils resulting from sunflower, maize or rape, containinga high content of linoleic acid, linolenic oils from linseed, comprisingsignificant contents of triunsaturated alkyl chains containing from upto 18 carbon atoms, and ricinoleic oils resulting from the castor oilplant.

Among the glycerol monoesters and diesters obtained from polycyclicacids, the preferred monoesters and diesters comprise an R₁ or R₃ and/orR₄ composed of at least two rings, each formed of 5 to 6 atoms, at mostone of which is optionally a heteroatom, such as nitrogen or oxygen, andthe others are carbon atoms, these two rings additionally having twocarbon atoms in common, preferably vicinal, these said rings beingsaturated or unsaturated. These are preferably glycerol monoesters ofnatural resin acids obtained from the residues from the distillation ofnatural oils extracted from resinous trees, in particular resinousconifers.

Among these esters of resin acids according to the invention, preferenceis given to esters of abietic acid, of dihydroabietic acid, oftetrahydroabietic acid, of dehydroabietic acid, of neoabietic acid, ofpimaric acid, of laevopimaric acid and of parastrinic acid.

By adjusting the operating conditions for partial hydrolysis of theseoils, it is possible directly to obtain the mixture of glycerolmonoalkyl esters/dialkyl esters.

According to another form of the invention, it is possible to prepareglycerol alkyl esters by an esterification reaction between thecarboxylic acids described above and glycerol.

The esters and the amides of formula (II) can be easily obtained byreaction of an alcohol, amine and/or alkanolamine compound with anorganic acid, such as oleic acid, or a simple ester, such as methyloleate, the reaction being carried out under the conditions known per seby a person skilled in the art for esterification and amidationprocesses.

In a first embodiment, the alcohols used to obtain the compound (II) arechosen from the group composed of methanol, ethanol, propanol,isopropanol, butanol, isobutanol, pentanol or 2-ethylhexanol, and/oroxyalkylated alcohols of formula R(O—CH₂—CHR′)_(n)—OH, in which R is analkyl group containing 1 to 6 carbon atoms, R′ is hydrogen or an alkylgroup containing 1 to 4 carbon atoms and n an integer varying from 1 to5, such as methyl cellosolve, butyl cellosolve, butyl digol and1-butoxypropanol.

In a second embodiment, the primary or secondary amines used to obtainthe compound (II) are chosen from the group composed of methylamine,ethylamine, propylamine, butylamine, isobutylamine, 2-ethylhexylamine,decylamine, dodecylamine, stearylamine and oleylamine, N,N-diethylamine,N,N-dipropylamine, N,N-dibutylamine, N,N-di(2-ethylhexyl)amine,methyldecylamine, N-methyldodecylamine and N-methyloleylamine.

In a third embodiment, for the compound (II), use is made ofalkanolamines chosen from amines containing 1 to 18 carbon atomssubstituted by at least one hydroxylated, hydroxymethylated,hydroxyethylated or hydroxypropylated group, such as ethanolamine,diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine,triisopropanolamine, N-methylethanolamine,tris(hydroxymethyl)aminomethane, (N-hydroxyethyl)methylimidazoline or(N-hydroxyethyl)heptadecenylimidazoline.

The additives obtained by physical mixing according to the invention areused to improve the lubricating power of diesel fuels for ground vehicleengines, optionally as a mixture with at least one oxygen-containingcompound chosen from the group formed by alcohols, ethers and esters, aswell as with any additive used to improve the quality of fuel, such asdetergent, dispersing, antioxidizing and antifoaming additives or evenbiofuel.

A second subject of the invention corresponds to the fuels containingbetween 25 and 2500 ppm and preferably from 100 to 1000 ppm by weight ofat least one additive used according to the invention dispersed in adiesel fuel which are defined by ASTM standard D-975.

The examples below are given by way of illustration of the invention butdo not limit the scope thereof.

EXAMPLE I:

The object of the present example is to compare the lubricating power ofthe lubricity additives according to the invention with that of theknown lubricity additives with regard to wear under the HFRR (HighFrequency Reciprocating Rig) test conditions, as is described by thestandardized procedure CEC-F06-A96 in the SAE 932692 article by J. W.Hadley of the University of Liverpool.

The additives according to the invention will be referenced X_(i), whilethe comparative additives will be referenced T_(i).

A first additive T₁ is the product of the reaction of oleic acid withdiethanolamine. This reaction is carried out in a 500 ml four-neckedround-bottomed flask into which are introduced first 84.6 g of oleicacid and 105.3 g of xylene and then 31.5 g of diethanolamine over aperiod of 10 minutes. The entire mixture is subsequently maintainedunder reflux in xylene for 6 hours in order to remove 6.4 ml of water.The final product obtained contains 50% of active material with anorangey-yellow colour. Analysis by infrared spectroscopy exhibitsabsorption bands at 3500 cm⁻¹, at 1730 cm⁻¹ and at 1650 cm⁻¹,corresponding respectively to the hydroxyl, ester and amide functionalgroups.

The second additive T₂ is the product of the reaction of a tall-oil acidand of diethanolamine. The tall-oil acid used is a combination of 70% ofa mixture of fatty acids (55% oleic acid, 38% linoleic acid, 5% palmiticacid and 2% of linolenic acid) and of 30% of resin acids exhibiting anacid number of 185 mg of KOH per gram. The reaction is carried out asfor T₁ by introducing 80 g of tall-oil acid, 28.2 g of diethanolamineand 98.6 g of xylene successively into the round-bottomed flask and bymaintaining reflux in xylene for 6 hours. The final reaction product isa clear, viscous, orangey-yellow liquid having a residual acid number of0.21 mg of KOH per gram.

The third additive T₃ is a mixture of glycerol alkyl esters, mono-, di-and trialkyl esters, mainly comprising glycerol monooleate.

The first additive according to the invention X₁ is a physical mixtureof 2 g of the additive T₂ and 1 g of the additive T₃.

The second additive according to the invention X₂ is a physical mixtureof 2 g of the additive T₁ and 1 g of the additive T₃.

The additive T₄ is the glycerol trioleate sold by the company Fluka.

The third additive according to the invention X₃ is the product of thereaction of gylcerol trioleate T₄ with diethanolamine. The reaction iscarried out in a four-necked round-bottomed flask, as for T₁, by mixing80 g of glycerol trioleate and 18.5 g of diethanolamine and by thenheating the entire mixture at 150° C. for 4 hours.

The additive T₅ is a soybean triglyceride oil with an average molecularmass of approximately 870, composed of 28% of oleic acid, 50% oflinoleic acid, 8% of linolenic acid, 3% of stearic acid, 10% of palmiticacid and 1% of arachidic acid.

The fourth additive according to the invention X₄ is the product of thereaction of 87 g of T₄ with 21 g of diethanolamine, the mixture beingkept stirred at 150° C. for 6 hours. The additive X₄ is a fluid,orangey-yellow liquid exhibiting, by infrared spectrometry, theabsorption bands characteristic of the alcohol, ester and amidefunctional groups.

The fifth additive according to the invention X₅ is obtained under thesame conditions as the additive X₄ but by using 87 g of T₄ and 15.75 gof diethanolamine.

The sixth additive according to the invention X₆ is obtained under thesame conditions as the additive X₄ but by using 27 g of the additive T₅and 26 g of diethanolamine.

The seventh additive according to the invention X₇ is obtained under thesame conditions as the additive X₄ but by replacing diethanolamine by 24g of tris(hydroxymethyl)aminomethane.

The eighth additive according to the invention X₈ is obtained under thesame conditions as the additive X₄ but by using, as triglyceride, castoroil with an average molecular mass of approximately 927 composed of 87%of ricinoleic acid, 7% of oleic acid and 3% of stearic acid.

Each of the additives described above is introduced into three differentdiesel oils A, B and C, the characteristics of which are given in TableI below, at a content of 100 ppm of active material.

TABLE I Diesel Diesel Diesel oil A oil B oil C Distillation (NFM 07-022)183 165 168.5 Point, initial Point at 10% volume 227 208.5 208 20%volume 247 227.5 226 50% volume 290 276 274.5 80% volume 334 317.5 31790% volume 354 334 336 Point, final 373 357.5 364 Density at 15° C.0.8508 0.8360 0.8364 (NFT 60-172) Calculated cetane number 51.3 50 53(ASTM D4737) % Sulphur (ppm) 480 270 455 HFRR lubricating power 425 772550 (CEC F06A96) (μm)

The diesel oils A, B and C, thus treated with additives, were subjectedto the HFRR test, which consists in jointly applying, to a steel ball incontact with a motionless metal plate, a pressure corresponding to aweight of 200 g and an alternating movement of 1 mm at a frequency of 50Hz. The moving ball is lubricated by the test composition. Thetemperature is maintained at 60° C. throughout the duration of the test,that is to say 75 min. The lubricating power is expressed by the meanvalue of the diameters of the wear imprint of the ball on the plate. Asmall wear diameter indicates a good lubricating power; conversely, alarge wear diameter expresses a power which becomes increasinglyinsufficient as the wear diameter increases.

TABLE II DIESEL OIL 1 DIESEL OIL 2 DIESEL OIL 3 Wear Wear Wear diameterGain diameter Gain diameter Gain ADDITIVES (μm) (%) (μm) (%) (μm) (%)Without 425 712 550 additive T₁ 335 21 618 20 456 17 T₂ 320 25 695 10470 15 T₃ 360 15 633 18 430 22 X₁ 301 29 525 32 396 28 X₂ 299 30 553 28439 20 T₄ 420 1 820 −6 — — X₃ 304 28 526 32 435 21 T₅ 410 4 750 3 545 1X₄ 291 32 501 35 405 26 X₅ 308 28 — — 442 20 X₆ 258 39 562 27 409 26 X₇331 22 444 42 440 20 X₈ 300 30 526 32 404 26

It is found, from this Table II, that the physical mixtures according tothe invention, such as X₁ and X₂, have wear characteristics which aresmaller and thus clearly better than those of T₁, T₂ and T₃, whichexpresses the synergistic effect obtained by combination of thepredominant components of the lubricity additive according to theinvention. X₃ corresponds to the reaction product obtained according tothe process of the invention from diethanolamine with glyceroltrioleate. As above, the advantage of the additive thus obtained withregard to the wear characteristics obtained with T₄ is perceived.

The performances of the additives X₄, X₅, X₆ and X₇ are to be comparedwith those of the starting oil T₅. As above, the combination of thereaction products limits the wear phenomena observed in the case of theoil alone.

What is claimed is:
 1. A fuel suitable for use in a diesel and/oraviation engine, having a sulphur content of less than or equal to 500ppm, and comprising an additive which comprises: from 5 to 25% by weightof at least one glycerol monoester of following formulae (I_(A)) or(I_(B)):

 wherein R₁ is selected from the group consisting of saturated orunsaturated, linear or slightly branched, alkyl chains comprising from 8to 24 carbon atoms and cyclic and polycyclic groups comprising from 8 to60 carbon atoms; from 35 to 75% by weight of at least one compound offormula (II) below:

 wherein R₂ is a saturated or unsaturated, linear or slightly branched,alkyl chain comprising from 8 to 24 carbon atoms, and X is selected fromthe group consisting of (i) the groups OR₀, wherein R₀ is a hydrocarbonresidue comprising from 1 to 8 carbon atoms, optionally substituted byone or more ester groups, and (ii) the groups deriving fromalkanolamines with a linear or branched aliphatic hydrocarbon chaincomprising from 1 to 18 carbon atoms, and from 0.1 to 20% by weight ofat least one glycerol diester of formula (III_(A)) and/or (III_(B)):

 wherein R₃ and R₄ are identical or different and are selected from thegroup consisting of saturated or unsaturated, linear or slightlybranched, alkyl chains comprising from 8 to 24 carbon atoms and cyclicand polycyclic groups comprising from 8 to 60 carbon atoms.
 2. The fuelof claim 1, wherein the glycerol monoesters of formula (I) and thediesters of formula (III) with, respectively, R₁ or R₃ and R₄ consistingof an alkyl chain are selected from the group consisting of themonoesters and diesters obtained from the oils selected from the groupconsisting of lauryl oils originating from copra or palm, which are richin saturated alkyl chains containing 12 to 14 carbon atoms, palmiticoils resulting from palm, lard or tallow, containing a major amount ofsaturated alkyl chains containing 16 carbon atoms, linoleic oilsresulting from sunflower, maize or rape, containing a high content oflinoleic acid, linolenic oils from linseed, comprising significantcontents of triunsaturated alkyl chains containing up to 18 carbonatoms, and ricinoleic oils resulting from the castor oil plant.
 3. Thefuel of claim 1, wherein the glycerol monoesters of formula (I) and theglycerol diesters of formula (III) comprise R₁ or R₃ and/or R₄ composedof at least two rings, each formed of 5 to 6 atoms, at most one of whichis optionally a heteroatom, and the others are carbon atoms, these atomsrings additionally having two carbon atoms in common, these said ringsbeing saturated or unsaturated.
 4. The fuel of claim 3, wherein saidheteroatoms are selected from the group consisting of nitrogen andoxygen.
 5. The fuel of claim 3, wherein said two carbon atoms in commonare vicinal.
 6. The fuel of claim 3, wherein the glycerol monoesters anddiesters of formulas (I) and (III) are obtained from natural resin acidscontained in the residues from the distillation of natural oilsextracted from resinous trees.
 7. The fuel of claim 5, wherein theesters of resin acids are selected from the group consisting of estersof abietic acid, dihydroabietic acid, tetrahydroabietic acid, ofdehydroabietic acid, neoabietic acid, pimaric acid, laevopimaric acidand parastrinic acid.
 8. The fuel of claim 1, wherein the esters and theamides of formula (II) are obtained by reaction of an alcohol and/oralkanolamine compound with a carboxylic acid or methyl oleate.
 9. Thefuel of claim 8, wherein said carboxylic acid is oleic acid.
 10. Thefuel of claim 8, wherein the alcohol is selected from the groupconsisting of methanol, ethanol, propanol, isopropanol, butanol,isobutanol, pentanol or 2-ethylhexanol and/or oxyalkylated alcohols offormula R(O—CH₂—CHR′)_(n)—OH, wherein R is an alkyl group containing 1to 6 carbon atoms, R′ is hydrogen or an alkyl group containing 1 to 4carbon atoms and n an integer varying from 1 to
 5. 11. The fuel of claim10, wherein the oxyalkylated alcohol is selected from the groupconsisting of methyl cellosolve, butyl cellosolve, butyl digol and1-butoxypropanol.
 12. The fuel of claim 6, wherein said resinous tree isa conifer.
 13. The fuel of claim 8, wherein the alkanolamine is selectedfrom the group consisting of amines comprising from 1 to 18 carbonsatoms substituted by at least one hydroxylated, hydroxymethylated,hydroxyethylated or hydroxypropylated group.
 14. The fuel of claim 13,wherein said alkanolamine is selected from the group consisting ofethanolamine, diethanolamine, triethanolamine, isopropanolamine,diisopropanolamine, triisopropanolamine, N-methylethanolamine,tris(hydroxymethyl)aminomethane, (N-hydroxyethyl)methylimidazoline and(N-hydroxyethyl)heptadecenylimidazoline.
 15. A method of making the fuelof claim 1, comprising incorporating the additive into a fuel.
 16. Afuel for vehicle engines, wherein the fuel comprises 25 to 2500 ppm ofan additive which comprises: from 5 to 25% by weight of at least oneglycerol monoester of formulae (I_(A)) or (I_(B)):

 wherein R₁ is selected from the group consisting of saturated orunsaturated, linear or slightly branched, alkyl chains comprising from 8to 24 carbon atoms and cyclic and polycyclic groups comprising from 8 to60 carbon atoms; from 35 to 75% by weight of at least one compound offormula (II) below:

 wherein R₂ is a saturated or unsaturated, linear or slightly branched,alkyl chain comprising from 8 to 24 carbon atoms, and X is selected fromthe group consisting of (i) the groups OR₀, wherein R₀ is a hydrocarbonresidue comprising from 1 to 8 carbon atoms, optionally substituted byone or more ester groups, and (ii) the groups deriving fromalkanolamines with a linear or branched aliphatic hydrocarbon chaincomprising from 1 to 18 carbon atoms, and from 0.1 to 20% by weight ofat least one glycerol diester of formula (III_(A)) and/or (III_(B)):

 wherein R₃ and R₄ are identical or different and are selected from thegroup consisting of saturated or unsaturated, linear or slightlybranched, alkyl chains comprising from 8 to 24 carbon atoms and cyclicand polycyclic groups comprising from 8 to 60 carbon atoms.
 17. The fuelof claim 16, wherein the fuel comprises 100 to 1000 ppm by weight of theadditive.
 18. The fuel of claim 16, which has a low sulfur content ofless than or equal to 500 ppm.
 19. The fuel of claim 16, which is adiesel fuel which satisfies ASTM standard D-975.